Ischemic stroke injury is mediated by aberrant Cdk5.

Ischemic stroke is one of the leading causes of morbidity and mortality. Treatment options are limited and only a minority of patients receive acute interventions. Understanding the mechanisms that mediate neuronal injury and death may identify targets for neuroprotective treatments. Here we show that the aberrant activity of the protein kinase Cdk5 is a principal cause of neuronal death in rodents during stroke. Ischemia induced either by embolic middle cerebral artery occlusion (MCAO) in vivo or by oxygen and glucose deprivation in brain slices caused calpain-dependent conversion of the Cdk5-activating cofactor p35 to p25. Inhibition of aberrant Cdk5 during ischemia protected dopamine neurotransmission, maintained field potentials, and blocked excitotoxicity. Furthermore, pharmacological inhibition or conditional knock-out (CKO) of Cdk5 prevented neuronal death in response to ischemia. Moreover, Cdk5 CKO dramatically reduced infarctions following MCAO. Thus, targeting aberrant Cdk5 activity may serve as an effective treatment for stroke.

Pulmonary surfactant protein A and surfactant lipids upregulate IRAK-M, a negative regulator of TLR-mediated inflammation in human macrophages.

Alveolar macrophages (AMs) are exposed to frequent challenges from inhaled particulates and microbes and function as a first line of defense with a highly regulated immune response because of their unique biology as prototypic alternatively activated macrophages. Lung collectins, particularly surfactant protein A (SP-A), contribute to this activation state by fine-tuning the macrophage inflammatory response. During short-term (10 min-2 h) exposure, SP-A's regulation of human macrophage responses occurs through decreased activity of kinases required for proinflammatory cytokine production. However, AMs are continuously exposed to surfactant, and the biochemical pathways underlying long-term reduction of proinflammatory cytokine activity are not known. We investigated the molecular mechanism(s) underlying SP-A- and surfactant lipid-mediated suppression of proinflammatory cytokine production in response to Toll-like receptor (TLR) 4 (TLR4) activation over longer time periods. We found that exposure of human macrophages to SP-A for 6-24 h upregulates expression of IL-1 receptor-associated kinase M (IRAK-M), a negative regulator of TLR-mediated NF-κB activation. Exposure to Survanta, a natural bovine lung extract lacking SP-A, also enhances IRAK-M expression, but at lower magnitude and for a shorter duration than SP-A. Surfactant-mediated upregulation of IRAK-M in macrophages suppresses TLR4-mediated TNF-α and IL-6 production in response to LPS, and IRAK-M knockdown by small interfering RNA reverses this suppression. In contrast to TNF-α and IL-6, the surfactant components upregulate LPS-mediated immunoregulatory IL-10 production, an effect reversed by IRAK-M knockdown. In conclusion, these data identify an important signaling regulator in human macrophages that is used by surfactant to control the long-term alveolar inflammatory response, i.e., enhanced IRAK-M activity.

Striatal dysregulation of Cdk5 alters locomotor responses to cocaine, motor learning, and dendritic morphology.

Motor learning and neuro-adaptations to drugs of abuse rely upon neuronal signaling in the striatum. Cyclin-dependent kinase 5 (Cdk5) regulates striatal dopamine neurotransmission and behavioral responses to cocaine. Although the role for Cdk5 in neurodegeneration in the cortex and hippocampus and in hippocampal-dependent learning has been demonstrated, its dysregulation in the striatum has not been examined. Here we show that strong activation of striatal NMDA receptors produced p25, the truncated form of the Cdk5 co-activator p35. Furthermore, inducible overexpression of p25 in the striatum prevented locomotor sensitization to cocaine and attenuated motor coordination and learning. This corresponded with reduced dendritic spine density, increased neuro-inflammation, altered dopamine signaling, and shifted Cdk5 specificity with regard to physiological and aberrant substrates, but no apparent loss of striatal neurons. Thus, dysregulation of Cdk5 dramatically affects striatal-dependent brain function and may be relevant to non-neurodegenerative disorders involving dopamine neurotransmission.

Modulation of glutamatergic transmission by sulfated steroids: role in fetal alcohol spectrum disorder.

It is well established that sulfated steroids regulate synaptic transmission by altering the function of postsynaptic neurotransmitter receptors. In recent years, evidence from several laboratories indicates that these agents also regulate glutamatergic synaptic transmission at the presynaptic level in an age-dependent manner. In developing neurons, pregnenolone sulfate (PREGS) increases the probability of glutamate release, as evidenced by an increase in the frequency of AMPA receptor-mediated miniature excitatory postsynaptic currents and a decrease in paired-pulse facilitation. In hippocampal slices from postnatal day 3-5 rats, this effect is mediated by an increase in Ca(2+) levels in the axonal terminal that depends on presynaptic NMDA receptors. This is followed by delayed potentiation of postsynaptic AMPA receptor currents. Importantly, depolarization of postsynaptic neurons, inhibition of hydroxysteroid sulfatase activity and acute exposure to ethanol mimics the effect of exogenous PREGS application. This developmental form of synaptic plasticity cannot be observed in slices from rats older than postnatal day 6, when presynaptic NMDA receptors are no longer expressed in CA1 hippocampal region. Both in the CA1 hippocampal region and the dentate gyrus of more mature rats, PREGS, dehydroepiandrosterone sulfate and hydroxysteroid sulfatase inhibitors increase paired-pulse facilitation, without affecting basal glutamate release probability. This effect depends on activation of sigma(1)-like receptors and G(i/o) and involves a target in the release machinery that is downstream of residual Ca(2+). These presynaptic actions of sulfated steroids could play important roles in physiological processes ranging from synapse maturation to learning and memory, as well as pathophysiological conditions such as fetal alcohol spectrum disorder.

Pyrethroid modulation of spontaneous neuronal excitability and neurotransmission in hippocampal neurons in culture.

Pyrethroid insecticides have potent actions on voltage-gated sodium channels (VGSC), inhibiting inactivation and increasing channel open times. These are thought to underlie, at least in part, the clinical symptoms of pyrethroid intoxication. However, disruption of neuronal activity at higher levels of organization is less well understood. In order to characterize pyrethroid effects on neurotransmitter release and neuronal excitability in glutamatergic networks, we examined the effects of deltamethrin (DM) and permethrin (PM) on neuronal activity in hippocampal neuronal cultures using patch-clamp and microelectrode array (MEA) recordings. In the presence of inhibitors of GABA receptors, spontaneous excitatory post-synaptic currents (sEPSCs) and spontaneous spike rates were reduced in a concentration-dependent manner by both DM and PM. IC(50) values were 0.037 and 0.70microM for inhibition of sEPSCs and 0.60 and 21.8microM for inhibition of spontaneous spike rate by DM and PM, respectively. Both compounds altered burst activity by decreasing the number of spikes during spontaneous bursting, the number of sEPSCs within a bursting release event and the duration of sEPSC bursts while increasing both the interspike interval and the time between sEPSCs. Exposure of neurons to the VGSC-specific modulator veratridine had effects similar to both DM and PM, while inhibition of voltage-gated calcium channels had no effect on spontaneous spike rates. In the absence of GABA receptor antagonists, both DM and PM increased spontaneous spike rates. Altogether, these data demonstrate that DM and PM disrupt network activity in vitro, largely via a VGSC-dependent mechanism.

Permethrin, but not deltamethrin, increases spontaneous glutamate release from hippocampal neurons in culture.

Pyrethroid insecticide modulation of the voltage-gated sodium channel (VGSC) is proposed to underlie their effects on neuronal excitability. However, some in vitro evidence indicates that target sites other than VGSCs could contribute to pyrethroid disruption of neuronal activity. VGSC-independent, pyrethroid-induced changes in neurotransmitter release were examined to investigate the possibility that target sites other than VGSCs contribute to pyrethroid effects. Using whole-cell patch clamp recordings, deltamethrin and permethrin effects on glutamate-mediated miniature excitatory postsynaptic currents (mEPSCs) from pyramidal neurons in mixed hippocampal cultures were examined. In the presence of the VGSC antagonist tetrodotoxin, the type I pyrethroid permethrin (10 microM) increased the average frequency of mEPSCs from a basal level of 1.0+/-0.4 to 3.5+/-0.6 Hz, with peak frequency of 9.9+/-1.5 Hz (n=6). Permethrin did not affect the distribution of current amplitudes, indicating that permethrin increased the probability of glutamate release at the presynaptic terminal without effects on postsynaptic responses. Removal of calcium from the extracellular solution following the induction of the permethrin-mediated effect decreased mEPSC frequency (6.8+/-1.8 Hz, n=3) to near control levels (1.9+/-0.8 Hz for control versus 2.5+/-0.6 Hz for permethrin minus Ca(2+), respectively). However, the N- and P/Q-type voltage-gated calcium channel antagonist omega-conotoxin MVIIC had no effect on the permethrin-dependent increase in mEPSC frequency. In contrast to permethrin, the type II pyrethroid deltamethrin (10 microM) failed to affect mEPSC frequency. These results indicate that permethrin causes a calcium-dependent increase in glutamate release from hippocampal neurons that is independent of effects on voltage-gated sodium or N- or P/Q-type voltage-gated calcium channels. The data indicate that permethrin increases mEPSC frequency via an alteration in intracellular calcium dynamics at the presynaptic terminal.

Developmental neurotoxicity of pyrethroid insecticides: critical review and future research needs.

Pyrethroid insecticides have been used for more than 40 years and account for 25% of the worldwide insecticide market. Although their acute neurotoxicity to adults has been well characterized, information regarding the potential developmental neurotoxicity of this class of compounds is limited. There is a large age dependence to the acute toxicity of pyrethroids in which neonatal rats are at least an order of magnitude more sensitive than adults to two pyrethroids. There is no information on age-dependent toxicity for most pyrethroids. In the present review we examine the scientific data related to potential for age-dependent and developmental neurotoxicity of pyrethroids. As a basis for understanding this neurotoxicity, we discuss the heterogeneity and ontogeny of voltage-sensitive sodium channels, a primary neuronal target of pyrethroids. We also summarize 22 studies of the developmental neurotoxicity of pyrethroids and review the strengths and limitations of these studies. These studies examined numerous end points, with changes in motor activity and muscarinic acetylcholine receptor density the most common. Many of the developmental neurotoxicity studies suffer from inadequate study design, problematic statistical analyses, use of formulated products, and/or inadequate controls. These factors confound interpretation of results. To better understand the potential for developmental exposure to pyrethroids to cause neurotoxicity, additional, well-designed and well-executed developmental neurotoxicity studies are needed. These studies should employ state-of-the-science methods to promote a greater understanding of the mode of action of pyrethroids in the developing nervous system.

Medication reconciliation at an academic medical center: implementation of a comprehensive program from admission to discharge.

PURPOSE: The implementation of a comprehensive medication reconciliation program to reduce errors in admission and discharge medication orders at an academic medical center is described. SUMMARY: A multidisciplinary team was formed to assess the current process of obtaining medication histories and to develop a new workflow for the pharmacist to obtain and reconcile medication histories. Pharmacists received intensive training on the new workflow, policies, and procedures. Hospitalwide multidisciplinary education was provided, and the new process was introduced in November 2005. Every inpatient admitted to the hospital has a complete and comprehensive home medication history interview conducted by a pharmacist or designee (pharmacy student or intern with subsequent verification by a pharmacist) within 24 hours of arrival. All components of the medication history are documented utilizing an integrated electronic medical record (EMR) medication documentation tool. Development of the discharge medication reconciliation program began in fall 2006. A discharge medication reconciliation report form was created through the EMR to improve the accuracy of the discharge medication orders. The form provides physicians with complete, accurate medication information and decreases the risk for transcription errors. Finally, a discharge medication report was developed for patients to take home. Analysis of the discharge reconciliation process revealed that medication errors were reduced from 90% to 47% on the surgical unit (95% confidence interval [CI], 42-53%; p = 0.000) and from 57% to 33% on the medicine unit (95% CI, 28-38%; p = 0.000). CONCLUSION: A pharmacy-driven multidisciplinary admission history and medication reconciliation process has reduced medication errors in an academic medical center.

Effects of pyrethroids on voltage-sensitive calcium channels: a critical evaluation of strengths, weaknesses, data needs, and relationship to assessment of cumulative neurotoxicity.

The Food Quality Protection Act of 1996 requires that the U.S. Environmental Protection Agency conduct cumulative risk assessments for classes of pesticides that have a common mode or mechanism of action. For the pyrethroid insecticides, disruption of voltage-sensitive sodium channel function is generally accepted as the mechanism underlying acute neurotoxicity. However, data exist which suggest that voltage-sensitive calcium (Ca(2+)) channels (VSCC) may also be important targets of pyrethroid action. VSCC are important to neuronal function during development and for neurotransmitter release, gene expression, and electrical excitability in the nervous system. Disruption of these and other processes mediated by VSCC can result in neurotoxicity. If effects on VSCC are demonstrated to contribute to pyrethroid neurotoxicity, then such effects will have to be considered when making decisions regarding cumulative risk of exposure to this class of compounds. This document provides a critical review of the data related to the hypothesis that VSCC are important targets of pyrethroid effects. Data supporting effects of pyrethroids on VSCC have been generated by several different laboratories using different techniques and biological preparations. Thus, the many reports of effects on VSCC provide evidence that pyrethroids may interact with VSCC. However, evidence to support a role of VSCC in pyrethroid neurotoxicity is based entirely on in vitro observations, and numerous limitations exist in these data, including: (1) lack of defined concentration-response relationships, with some effects observed only at relatively high concentrations, (2) the use of indirect measures of VSCC function, (3) data from nonmammalian species, (4) data from studies that have not been peer-reviewed, (5) the need for replication of some effects, and (6) inconsistent or contradictory results from different laboratories/preparations. Thus, at the present time, it is premature to conclude that effects on VSCC play an important role in the acute neurotoxicity of pyrethroid insecticides in mammals. To demonstrate that VSCC are important targets of pyrethroid neurotoxicity in mammals, in vivo studies supporting a role for pyrethroid effects on VSCC are needed. Additional support could be provided by demonstration of direct effects of pyrethroid compounds on mammalian neuronal VSCC in vitro, including demonstration that concentration-response relationships are similar, or greater, in sensitivity to effects of pyrethroids on voltage-sensitive sodium channels. If such effects were to be demonstrated, the rationale for considering VSCC as targets of pyrethroid compounds when assessing cumulative risk would be strengthened. However, at the present time, the data available neither support nor refute conclusively the hypothesis that effects on VSCC are important to the acute neurotoxicity of pyrethroids.

Neurosteroids enhance spontaneous glutamate release in hippocampal neurons. Possible role of metabotropic sigma1-like receptors.

Pregnenolone sulfate (PREGS), one of the most abundantly produced neurosteroids in the mammalian brain, improves cognitive performance in rodents. The mechanism of this effect has been attributed to its allosteric modulatory actions on glutamate- and gamma-aminobutyric acid-gated ion channels. Here we report a novel effect of PREGS that could also mediate some of its actions in the nervous system. We found that PREGS induces a robust potentiation of the frequency but not the amplitude of miniature excitatory postsynaptic currents (mEPSCs) mediated by alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptors in cultured hippocampal neurons. PREGS also decreased paired pulse facilitation of autaptic EPSCs evoked by depolarization, indicating that it modulates glutamate release probability presynaptically. PREGS potentiation of mEPSCs was mimicked by dehydroepiandrosterone sulfate and (+)-pentazocine but not by (-)-pentazocine, the synthetic (-)-enantiomer of PREGS or the inactive steroid isopregnanolone. The sigma receptor antagonists, haloperidol and BD-1063, blocked the effect of PREGS on mEPSCs, as did pertussis toxin and the membrane-permeable Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (acetoxymethyl) ester. These results suggest that PREGS increases spontaneous glutamate release via activation of a presynaptic G(i/o)-coupled sigma receptor and an elevation in intracellular Ca2+ levels. We postulate that presynaptic actions of neurosteroids have a role in the maturation and/or maintenance of synaptic networks and the processing of information in the central nervous system.